Physicists have designed a laser defence system to cloak Earth from bad-guy aliens

4/01/2016

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We humans are pretty into the idea of finding
aliens, but have we really thought through what would happen if we stumbled
across extraterrestrial intelligence that didn't want to 'come in peace', and
instead was hell-bent on mining our fair planet for everything it's got? No? Well, luckily for us reckless daydreamers,
astronomers have our back, and have come up with a pretty solid plan that would
cloak our planet from any bad-guy aliens out there looking for us. And it
relies entirely on lasers (what else?).

So how does it work? In order to find planets
outside our Solar System, we watch other stars and look for signs
of their light dimming periodically, which indicates that a planet is
passing in front of them. By watching how often a planet crosses its sun,
and how
much light it blocks, we can get a pretty good idea of how close the planet
is to its star, and how big it is. And because we can't possibly examine every
planet in the Universe, we use that information to work out which might be
most interesting to us. So for humans, that's planets that might contain water, or
could be habitable.

Assuming big-bad aliens use a similar technique to
look for planets that interestthem, we'd have to find a way to stop
them from noticing Earth as it passes in front of the Sun if we wanted to stay
off their radar - and that's where the lasers come into it.

A team from Columbia University has now proposed a
system that would fire a laser at the precise moment Earth crosses in front of
the Sun, so that stars lying along the same plane wouldn't even notice the
light dimming.

The idea started off as an attempt to alter the
signal we were broadcasting about our planet's orbit into space, but then the
team realised we could actually cloak our planet entirely if we wanted.

In order to hide our existence in terms of optical
wavelengths - so that no one could see us - the astronomers calculate that we'd
need to blast a 30 megawatt laser for about 10 hours once a year.

We could also scale things up and use an array of
tuneable lasers that would cloak us on all wavelengths, rendering us invisible,
but that would require around 250 megawatts of power.

Doing that could also make us seem more suspicious
for any aliens looking closely, as there'd still be indirect traces of our
planet, such as the way it affects the orbits of the rest of the planets in our
Solar System. So a total cloaking system could actually make us even more
interesting to extraterrestrial lifeforms.

A more efficient (and safer) plan, the researchers
report, would be to only cloak the atmospheric signals associated with
biological activity, such as oxygen and water vapour. That would only take up
about 160 kilowatts of energy, and would make our planet look pretty
uninteresting to any onlookers with questionable intentions.

"The atmospheric cloaking produces totally
self consistent observations," co-author Alex
Teachey told Gizmodo. "They see a planet, but they think it’s a just
another dead world floating out in space."

The plan's not foolproof, because we have no idea
what kind of technology extraterrestrial life might have, or how they could be
searching for other lifeforms in space - if they're looking for us at all. (And
hopefully it goes without saying that aliens aren't necessarily going to be
bad.)

But the good thing is, we already have all the
technology - and energy - available to put it in place. "We could
build this next week if we really wanted to," added
Teachey. "It’s totally feasible with current technology."

That all sounds great, but it does make you
wonder... if we can cloak our planet from aliens, then what's to say they're
not doing the same to us? Mind = blown.